Dust and other particulate matter can present significant hazards to the operators of rotary wing aircraft. In this specification “other particulate matter” includes sand, snow, water droplets, stones, pebbles, grass, twigs, soil, litter, and any other small loose items. During take-off and landing, and during near-ground hovering, clouds of dust or other particles can be generated around a helicopter. This can result in loss of visibility or “brown-out” in the case of dust or sand, or “white-out” in the case of snow. Particles can clog the air intakes of an aircraft's engines, resulting in overheating, and fine particles ingested through the engines can cause damage and mechanical failures. Particles can cause accelerated wear-and-tear on rotors and rotor gear. Coarser airborne particles can cause eye injuries and other types of injuries to people near the aircraft, and other aircraft, vehicles, equipment and facilities in the area can be damaged.
Helicopter landing pads are typically constructed from concrete, asphalt, bitumen or another solid surface. When, however, it is necessary to land at a site which does not have a solid landing pad, problems with dust and other particles often arise. One solution has been to create a portable landing pad, and such portable landing pads are typically made from steel or some other strong, and relatively solid and heavy material which is not likely to be blown away by the helicopter's downdraft. However, such landing pads are very cumbersome to move around, and are unsuitable for rapid deployment.
One manner of constructing a short-term helicopter landing pad on a dusty or sandy surface involves spraying the surface with water. The effectiveness of this technique depends on having sufficient water available, and the landing surface ceases to be usable once the water dries, which may only be a matter of minutes in some environments. A longer term landing pad may be created using sump oil, diesel fuel or another non-volatile liquid, but the effectiveness is still short-lived, it is necessary to have a supply of oil or diesel fuel available, and the environmental damage is significant. A more environmentally friendly solution is provided by a product known as Envirotac II, or “Rhino Snot”, but this still requires a supply to be available when needed.
Landing pads are typically not made out of cloth materials such as canvas or PVC tarpaulins, because of the dangers associated with the cloth flapping up and getting caught in the helicopter's rotors. Even if a canvas tarpaulin were firmly anchored down on every side, there is still the possibility that in a heavy landing a helicopter's skids or wheels might tear the canvas, especially when the ground contains some exposed rock, and the helicopter's downdraft on the torn portion of the canvas would cause air to flow under the canvas, lifting the canvas, causing additional strain on the anchor points, and accentuating the tear, with the attendant risk that a torn portion of the canvas will be caught up in the helicopter's rotors.
In some military operations, landing mats are made of aluminum sheet (which may be fabric-like, rather than rigid metal). Aluminum is less hazardous than canvas, but there are significant difficulties and dangers experienced with wind getting under the mats, or blowing the mats or pieces of mat around, resulting in injury to people on the ground as well as endangering the helicopter
A further problem associated with the use of a flexible landing pad arises from the effect of the helicopter's downdraft on the edges of the landing pad. As the helicopter's downdraft nears the ground, it is directed outwardly, so that the air flow near the edges of the landing pad is rapid and nearly horizontal. The rapidly flowing air on the top side of the landing pad has a lower pressure than the still air on the underside of the landing pad, and this causes the edges of the landing pad to flap up. In the past, this problem has been dealt with by making the edges of the landing pad so heavy that they cannot be moved by the airflow, but this significantly reduces the portability of the landing pad. Alternatively, large, heavy pegs are used to secure the landing pads, but these make the pads less portable and more time-consuming to set up or pack away.
The US Army has used a relatively light-weight temporary road-surfacing type of matting known as “Mobi-Mat,” which is a solid plastic material impermeable to air. It is typically stored in large rolls which are bulky and heavy, and in use the mats are held down by 1-meter pegs. Standard mat sizes are 4.2 m wide, 0.4 m thick, and 8 m, 12 m or 20 m long. The 8 m mats weigh 56.5 kg, the 12 m mats weigh 84 kg and the 20 m mats weigh 149 kg. Each mat therefore requires two or more people to carry it.